Is 'Cold-Solder' Spraying Sprinkler or Area Below?

Does 'cold solder' specifically mean that one sprinkler gets another wet, or does it mean that one sprinkler keeps the floor area cool enough so the adjacent sprinkler doesn't activate?

Or is it both?

I've recently had several conversations in which the other party was convinced that cold-soldering can​ only occur when one sprinkler wets and cools another sprinkler's thermal element.

I was taught a long time ago that cold-solder referred to one sprinkler keeping the floor area wet and cool but not wet enough to effectively put out or control a fire, thereby allowing the fire to 'skip' to the next sprinkler, allowing the fire to grow larger than had both adjacent sprinkler heads activated properly.

Obviously, if a sprinkler gets wet and does not activate, it causes the same problem. It makes a difference in my mind because, at soffits or varying ceiling elevations, the lower sprinkler could spray into the higher sprinkler's floor area. If the vertical change is 36" or greater, NFPA says to treat it as a wall, and sprinklers must be 1/2 x S from this plane.

In my mind, the differences in ceiling height would effectively create a baffle, and neither sprinkler would actually wet the other. However, if they were closer than 6'-0 measured on a flat horizontal plane, they would still be cold soldered since one sprays into the floor area of another. I see this all the time. Do you have thoughts on this?

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